How long shall we record electroencephalography?

BACKGROUND: The duration of electroencephalography (EEG) recordings varies widely among laboratories. Although several recommendations had been published, there are no previous studies directly addressing this. AIMS OF THE STUDY: To assess the effect of the recording duration on detection of EEG abnormalities in a tertiary referral centre for epilepsy. METHODS: We have reviewed 1005 EEG recordings and determined the shortest recording duration necessary to identify interictal EEG abnormalities. RESULTS: Standard, awake recordings shorter than 20 min yielded a significantly lower incidence of abnormal findings as compared to longer recordings. Although there was an increase in the diagnostic yield from 30 to 180 min recording duration, this failed to reach the level of significance. For sleep recordings, there was no significant increase in the diagnostic yield beyond 30 min. CONCLUSIONS: Our results provide evidence for recommending at least 20 min recording duration for standard awake EEGs and 30 min for sleep EEG recordings. As data were derived from patients referred to our epilepsy centre, the results are only valid for epilepsy-related indications.

Effectiveness of the ketogenic diet in a broad range of seizure types and EEG features for severe childhood epilepsies.

BACKGROUND: Ketogenic diet (KD) is an effective treatment for pharmacoresistant epilepsy: more than half of the patients show a greater than 50% reduction in seizures. OBJECTIVE: To identify clinical or electroencephalogram (EEG) variables predicting the response to KD. METHODS: Clinical and EEG data were retrospectively analysed from 50 consecutive patients treated by KD for severe, pharmacoresistant epilepsy. Most of the patients (70%) had retarded mental and motor development. RESULTS: Three months after the start of the KD two-thirds (33) of the patients were responders (had a more than 50% reduction in seizure frequency). The presence of epileptiform EEG discharges in the temporal region correlated with an unfavourable response (P = 0.03). The presence of bilateral synchronous epileptiform discharges, and the presence of complex partial seizures approached significance but all other variables did not. CONCLUSIONS: Our results further support that KD is efficient in a wide variety of epileptic patients with a broad range of EEG features. However, patients with epileptiform discharges in the temporal region are less likely to achieve therapeutic response.

The misdiagnosis of epilepsy in children admitted to a tertiary epilepsy centre with paroxysmal events.

AIMS: To determine the proportion of children admitted with difficult to treat paroxysmal events to a tertiary epilepsy centre who did not have epilepsy. METHODS: In an observational retrospective study, all case notes of 223 children admitted in 1997 were examined. The referral was made from the local paediatric department in 51% of cases, other departments in 27%, and from general or specialist practitioners in 22%. Doubt regarding the diagnosis of epilepsy was expressed in the referral note in 17%. On admission, 86% were on antiepileptic drug treatment. During admission all children were subjected to a comprehensive intensive observation and 62% had EEG monitoring. RESULTS: In total, 39% (87/223) were found not to have epilepsy. In 30% of children (55/184) referred without any doubts about the epilepsy diagnosis, the diagnosis was disproved. Of the 159 children admitted for the first time, 75 (47%) were discharged with a diagnosis of non-epileptic seizures. Of 125 children admitted for the first time with no doubts about the diagnosis of epilepsy, 44 (35%) did not have epilepsy. Staring episodes were the most frequently encountered non-epileptic paroxysmal event. Psychogenic non-epileptic seizures were found in 12 children. A total of 34 (15%) had their medication tapered off; a further 22 (10%) had tapered off medication before admission. CONCLUSION: The present study supports the view that misdiagnosis of epilepsy is common. The treating physician should be cautious in diagnosis, especially of staring episodes. A diagnostic re-evaluation should be undertaken in difficult cases with continuing paroxysmal events in order to avoid unnecessary drug treatment and restrictions on the child's lifestyle.

Characteristics and phenomenology of epileptic partial seizures in dogs: similarities with human seizure semiology.

Dogs with spontaneous occurring epilepsy with partial seizures express symptomatology resembling what is found in humans with partial epileptic seizures. Questionnaires on clinical signs from 70 dogs, with a confirmed diagnosis of epilepsy with partial seizures with or without secondary generalization, were reviewed in order to characterize and classify clinical signs of partial seizure activity in dogs and compare them to partial seizure phenomenology in humans. Signs of partial seizure activity were distributed into three categories: motor signs, autonomic signs and paroxysms of behavioral signs. Motor signs were described in 48 dogs (69%), autonomic signs in 16 dogs (23%) and paroxysms of behavioral signs in 56 dogs (80%). The majority of dogs expressed signs from more than one group. Sixty-one dogs (87%) had partial seizures with secondary generalization. Nine dogs (13%) had partial seizures without secondary generalization. The study shows a remarkable resemblance between the seizure phenomenology expressed in humans and canines with partial epileptic seizures.

Epilepsy and pregnancy: lamotrigine as main drug used.

OBJECTIVES: To study the risk of teratogenicity in infants of women with epilepsy. MATERIAL AND METHODS: Prospective data from 1996 to 2000 comprised 147 pregnancies. The most frequent antiepileptic drugs (AEDs) used were lamotrigine (LTG) 35% (n = 51), oxcarbazepine (OXC) 25% (n = 37) and valproate (VPA) 20% (n = 30). Seventy-four per cent (n = 109) received monotherapy. Folic acid supplementation was taken during first trimester by 118 patients (80%). RESULTS: The overall risk of malformations among newborns in the AED-exposed group was 3.1% (n = 4). Two children were born with multiple malformations (VPA monotherapy), two children had ventricular septal defects (one OXC monotherapy, and one OXC and LTG). The risk of malformations was 2.0% in women treated with LTG and 6.7% in women treated with VPA (NS). CONCLUSION: Despite the small number of cases in the study these data indicate that treatment with LTG during pregnancy might be relatively safe. Larger prospective studies are needed to obtain adequate power for statistical analysis.

Landau-Kleffner syndrome with onset at 18 months and an initial diagnosis of pervasive developmental disorder.

We report one of the youngest and most intensively studied cases of Landau-Kleffner syndrome, with a follow-up of 5 years. The boy developed normally until the age of 18 months when he had two attacks, possibly epileptic. Electroencephalogram (EEG) was normal. Over the next 5 months he lost his six to ten words, did not engage with other children and became mute. When he was 34 months old a child-psychiatrist suggested a diagnosis of pervasive developmental disorder or developmental dysphasia. An EEG 3 months later showed abnormalities typical of Landau-Kleffner syndrome. His non-verbal abilities were normal as well as his neurological examination and brain magnetic resonance imaging (MRI). A trial of clobazam and vigabatrin was unsuccessful. When he was 4 years and 9 months old he was treated with corticosteroids and within 3 months his vocabulary increased from the standard for 1 1/2 years of age to that for 2 1/2 years of age. His language abilities continued to improve slowly until a stagnation period at the age of 6 years and 9 months. A second course of corticosteroids improved his comprehension and vocabulary to an almost normal level, and his EEG normalized. A total of 11 EEGs were obtained; all included sleep, but continuous spike and wave during slow sleep was never documented. This report illustrates that Landau-Kleffner syndrome should be considered as an alternative diagnosis in children diagnosed with developmental dysphasia. An EEG including sleep should be considered, and in the presence of abnormalities a trial of anti-epileptic drugs or corticosteroids should be undertaken.

Changes in plasma GABA concentration during vigabatrin treatment of epilepsy: a prospective study.

The aim of the present prospective study was to evaluate changes in plasma GABA concentration in relation to clinical response during vigabatrin treatment of epilepsy. We studied 29 patients with uncontrolled partial-onset seizures during open add-on vigabatrin treatment and measured plasma GABA and vigabatrin concentrations by a sensitive HPLC method. Following short-term treatment 17 out of 28 patients had a seizure reduction of > 50% (responders). After long-term treatment 16 out of 22 patients were responders. There was no difference between responders and nonresponders regarding pretreatment seizure frequency, treatment duration, vigabatrin dose, or plasma vigabatrin concentration. Responders had a significant (p < 0.001) increase in mean plasma GABA both after short-term (from 0.380 to 0.530 nmol/ml; mean increase: 48%) and after long-term (from 0.392 to 0.618 nmol/ml; mean increase: 71%) vigabatrin treatment, whilst nonresponders had no significant changes in GABA levels. However, since plasma GABA increased in a subgroup of nonresponders, mean plasma GABA levels did not differ between responders and nonresponders. Although plasma GABA increased significantly in the responder but not in the nonresponder group during vigabatrin treatment of patients with epilepsy, it does not seem to be a reliable marker of individual clinical response to vigabatrin treatment.

[Congenital bilateral perisylvian syndrome]. / Kongenit bilateralt perisylvant syndrom.

The congenital bilateral perisylvian syndrome is characterized by pseudobulbar palsy, moderate delay in mental and motor development and epilepsy. Three characteristic case stories are presented. Epileptic seizures are most frequently generalized: tonic, astatic, atypical absences and tonic-clonic seizures. Partial seizures are less frequent. Seizure control is often unsatisfactory. Neuroimaging demonstrates thickening of the cerebral cortex in the perisylvian area bilaterally; these changes together with the clinical picture establish the diagnosis. The etiology is unknown.

Serum prolactin levels are elevated also after pseudo-epileptic seizures.

The aim of the study was to evaluate the sensitivity, specificity and the predictive values of repeated serum prolactin measurements in relation to epileptic seizures versus pseudoseizures. The method used was prospective measuring of serum prolactin from blood samples drawn (1) 15 min after seizure and (2) 2 hr after the first sample. Two parameters were used: the absolute maximal level; and the relative rise in blood level. In the study 38 had epilepsy (simple or complex partial seizures with or without secondary generalisation); and 20 had pseudo-epileptic seizures. In all cases, the diagnoses were made independent of the prolactin levels. In 30/38 (79%) of epilepsy patients and 17/20 (85%) of pseudoseizure patients, the diagnoses were corroborated by intensive EEG monitoring (video or cassette telemetry). There was a statistically significant rise in prolactin levels in both groups (p < 0.0001 and < 0.02, respectively), and also a significant difference between the two groups. However, repeated measurements in a number of patients (epilepsy: mean 1.5 measurements; pseudo; mean 2.1) showed also considerable intra-patient variations. The sensitivity for the maximal rise in pseudoseizures (5.5x) was only 20% and the negative predictive value 40%. For the cut-off in absolute level (1025 microU/ml), the corresponding figures were 34% and 44%, respectively. The rather limited discriminative power of prolactin measurements makes it of questionable value in discerning between epileptic and pseudo-epileptic seizures.

Long-term safety and efficacy of lamotrigine (Lamictal) in paediatric patients with epilepsy.

This study was initiated to evaluate the long-term safety, tolerability and effect on seizure control of lamotrigine (Lamictal) in paediatric patients with epilepsy. A total of 155 children (aged 2-19 years) with treatment-resistant epilepsy received add-on therapy or monotherapy lamotrigine for up to four years. Patients had already experienced benefit from lamotrigine treatment in an open one-year study before entering this open continuation study of up to three additional years of treatment. Overall, including both these studies, patients were treated with lamotrigine for 53-221 weeks, representing 417.9 patient-years of experience. The physician's global assessment of seizure control compared to the three-month period before lamotrigine treatment, indicated that seizure control was generally maintained during long-term lamotrigine treatment for up to four years. For 19 patients, the investigator recorded a subjective improvement in behaviour, alertness, seizure severity, quality of life and mobility with lamotrigine treatment, sometimes independent of seizure control. In total, 34 patients received lamotrigine monotherapy; 22 of these were maintained on lamotrigine monotherapy for at least one year. Lamotrigine was well tolerated. The majority of adverse experiences were classified by the physician as being mild in intensity and only six patients (4%) withdrew from the study due to adverse experiences.

Lamotrigine for the treatment of epilepsy in childhood.

OBJECTIVE: In this multicenter study, the efficacy and tolerability of lamotrigine were assessed in 285 children less than 13 years of age, recruited from 37 centers in 11 countries. METHODS: Pooled data from five open add-on studies have been analyzed. All the children had treatment-resistant epilepsy and most had two or more seizure types. Seizure frequency and global evaluation were assessed at the end of four successive 12-week periods of therapy. RESULTS: Seizure frequency was reduced by 50% or more in one third of the patients. Lamotrigine was effective in all seizure types examined, particularly for typical and atypical absence seizures. Atonic seizures also responded well. Improvement was well maintained during the treatment period. The maintenance dose had to be adjusted according to concomitant medication; dose ranges were 1 to 5 mg/kg per day for children taking valproate and 5 to 15 mg/kg per day for those not taking valproate. The commonest reported adverse experiences were somnolence, rash, vomiting, and seizure exacerbations. Adverse experiences led to withdrawal of treatment from 36 patients (12.6%). CONCLUSIONS: These results indicate that lamotrigine is well tolerated and is effective for a broad range of seizure types, especially absence seizures and atonic seizures.

Vigabatrin in childhood epilepsy: a 5-year follow-up study.

In an retrospective uncontrolled long-term study in 30 children with intractable epilepsy, it was found that treatment with vigabatrin resulted in a seizure reduction of more than 50% at 1-year follow-up in 40% of the children. The responders were all children with partial seizures. Side effects were mild and did not lead to discontinuation of the drug. Increased numbers of seizures were seen in three cases. A moderate weight increase was seen in 27% of the children. At 5-year follow-up 7 children (23%) still maintained a seizure reduction of more than 50%. Trials of monotherapy in three seizure-free patients were unsuccessful. No further side effects were observed. A study of evoked potentials in 12 children showed no alteration in latency and amplitudes of VEP following treatment with vigabatrin. Our results show that in children vigabatrin seems to have a stable effect even though a few children may experience a breakthrough of seizures. The presented results together with previous reports on MRI-scans seem to indicate that even in children with a still maturing CNS vigabatrin is a safe drug.

Extracranial EEG work-up in epilepsy surgery: usefulness and limitations.

Extracranial interictal and ictal EEG provide essential information to diagnosis, seizure/syndrome classification and focus localization. Combined with structural and dynamic neuro-imaging and neuropsychological data, extracranial EEG will often provide sufficient information in preoperative work-up for temporal lobectomy. Ictal EEG recordings are essential to confirm the diagnosis and classification and, above all, to exclude patients with significant non-epileptic seizures from further surgical evaluation. The advantage of sphenoidal electrodes lies first and foremost in a more favorable signal/noise ratio, while their superiority to closely placed special scalp electrodes are more debatable.

Pseudoseizures--risk factors and prognosis. A case-control study.

Risk factors and prognosis for pseudoseizures were studied in a matched pairs case-control investigation of Epilepsy Clinic out-patients. The case group comprised 28 patients with pseudoseizures, 4 of whom were without a prior diagnosis of epilepsy. The control group consisted of 28 age- and sex-matched epileptic patients. There was a marked female preponderance, 86%, in the group with pseudoseizures. The frequency of previous psychiatric problems was significantly higher in the case- than in the control group, while the factors major cerebral damage and idiopathic generalized epilepsy were significantly less prevalent. At follow-up, median 5.8 years after diagnosis of pseudoseizures, 45% of the patients in the case group were free from all types of seizures. A significantly higher proportion of cases, 55%, were living on public disablement pension, compared to 23% of control patients.

[Surgical treatment of epilepsy resistant to drug therapy. A review]. / Kirurgisk behandling af medikamentelt intraktabel epilepsi. En oversigt.

The prevalence of epilepsy is 7-9 cases per 1,000 population, corresponding to 440,000 individuals in Denmark. Approximately 1/4 of these individuals have seizures refractory to anticonvulsant medications and most of them have an epileptic focus in the temporal lobe. Epilepsy refractory to anticonvulsant medication is an incapacitating disease with high costs for the person and the society. The main problems are polypharmacy with side effects, suspicion of neurodegenerative consequences and a higher mortality. The modern era of epilepsy surgery began more than 100 years ago and since then, the developments in neurophysiology and neuroimaging have made it possible to demonstrate the epileptic focus with relatively high precision. As a consequence of this, the volume of the resected tissue has diminished and the operative complications become less frequent. The somatic and neuropsychological effects of a cortical resection are discrete and compensated by a general improvement in performance. Surgical treatment of epilepsy should no longer be considered as a last resort, but as a realistic treatment in cases of medication failure.

[3-year experiences with surgical treatment of epilepsy at the Hvidovre hospital]. / Tre års erfaringer med epilepsikirurgi på Hvidovre Hospital.

The results of a retrospective survey of 48 patients submitted to neurosurgery for medically intractable epilepsy are presented. Twenty-eight patients were treated with selective amygdalohippocampectomy, one with temporal lobe resection, 12 with anterior callosotomy and seven with a total callosotomy. Of the amygdalohippocampectomized patients and the one with temporal lobe resection (n = 29), 52% were seizure free, 17% experienced rare seizures, 7% had a worthwhile improvement while 24% observed no worthwhile improvement (follow-up time 6 to 36 months). Of the callosotomized patients, 11% were free from generalized seizures, 69% had a significant seizure reduction and 18% experienced no worthwhile improvement. The observed neurological complications were: one patient had hemianopia, one had superior quadrant anopia, four developed unilateral anosmia and one complete anosmia. The callosotomized patients, with two exceptions, were all mentally and physically handicapped. In the callosotomy group, two patients died, one from a intracerebral hematoma three months after the operation and another patient seven months postoperatively from unknown causes.

[Pseudoepileptic seizures in children]. / Pseudoepileptiske anfald hos børn.

Pseudoepileptic seizures (pseudoseizures) are defined as episodic disturbances of behaviour with elements of epileptic seizures, but with atypical features and not accompanied by abnormal EEG discharges. They are frequently seen in patients with epilepsy, but also as the only disturbance of function. In children, the possible pathogenetic mechanisms are less understood than in adults. We present a series of cases, showing that an important factor in development of pseudoseizures lies in disturbances of communication between children and parents within the family. However, there are large interindividual variations in the most probable underlying mechanisms. Some recommendations as regards treatment are given.